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OALib Journal期刊

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DINáMICA DEL NITRóGENO BAJO DIFERENTES ROTACIONES, SISTEMAS DE LABRANZA Y MANEJO DE RESIDUOS EN EL CULTIVO DE TRIGO
Vidal,Iván; Etchevers,Jorge; Fischer,Anthony;
Agricultura Técnica , 2002, DOI: 10.4067/S0365-28072002000100012
Abstract: the behavior of wheat (triticum aestivum) in distinct rotations, tillage systems and residue management were quantified, and the mineralization and absorption of nitrogen (n) under different management conditions were measured employing microlysimeters placed in the soil. three years after establishing treatments tending to make the wheat production system more manageable in a zone with summer rainfall, the incorporation of a legume in the rotation translated, in general, into better yields and better n supplies for the plant. this was explained by the occurence of greater mineralization of n in the soil, both during the crop?s growth period as well as at the moment of seeding as a consequence of the incorporation of residues in the rotation. in almost all cases, wheat cultivated as a monoculture had the lowest grain yield, however, the lowest soil n supply was observed in the corn-wheat rotation. zero tillage resulted to be good management practice in those years where water was a limiting factor for crop growth, however, no advantage of this practice was observed in normal rainfall years. conventional tillage always resulted in higher residual n measured at sowing as well as more n mineralized during the cropping period, which occurred to the detriment of n reserves in the soil. the practice of leaving or removing the prior crop residues did not produce any conclusive results, although it is hoped that the benefits will begin to be observed in future years. this practice, as well as zero tillage, however did produce a significant increase in the soil microbial biomass, which is considered as a positive biological indicator of the quality of the soil and the sustainability of the systems.
INVESTIGACION Y EXPERIENCIA DE TRABAJO COLABORATIVO CON PROFESORAS: UN SEGUIMIENTO DE LOS ALUMNOS
Orellana Etchevers,Eugenia; Bravo Valdivieso,Luis;
Estudios pedagógicos (Valdivia) , 2000, DOI: 10.4067/S0718-07052000000100006
Abstract: this article presents the application of a collaborative teaching model among specialists in special education and teachers in low s.e.s. children's groups, and a follow-up study of reading and verbal process in the first and the second grades. results show significant differences in reading comprehension and in verbal test between the experimental and the control groups in the second grade. in the fourth grade, as the collaborative teaching was over, significant differences between those groups did not appear.
DINáMICA DEL NITRóGENO BAJO DIFERENTES ROTACIONES, SISTEMAS DE LABRANZA Y MANEJO DE RESIDUOS EN EL CULTIVO DE TRIGO Dynamics of nitrogen under different rotations, tillage systems and residue management in wheat
Iván Vidal,Jorge Etchevers,Anthony Fischer
Agricultura Técnica , 2002,
Abstract: Se cuantificó el comportamiento del trigo (Triticum aestivum) en distintas rotaciones, sistemas de labranza y manejo de residuos y, se midió la mineralización y absorción de nitrógeno (N) bajo estas diferentes condiciones de manejo, empleando microlisímetros enterrados en el suelo. Después de tres a os de establecer ciertos tratamientos tendientes a hacer más sustentable el sistema de producción de trigo en una zona con régimen de lluvias de verano, la incorporación de una leguminosa en la rotación se tradujo, por lo general, en mayores rendimientos y mejor abastecimiento de N para la planta. Esto fue explicado por la ocurrencia de una mayor mineralización del N en el suelo, tanto durante el período de crecimiento del cultivo como por la presencia de más N residual al momento de la siembra, como consecuencia de la incorporación de residuos en la rotación. En casi todos los casos, el monocultivo de trigo resultó ser el tratamiento con el menor rendimiento, pero no con el menor suministro de N, lo cual si fue observado en la rotación maíz-trigo. La labranza cero resultó ser una buena práctica en un a o con restricciones hídricas durante el ciclo de crecimiento del trigo, pero no se observaron ventajas en un a o cercano al normal. La labranza convencional invariablemente presentó mayor N acumulado al momento de la siembra y mineralización del mismo durante el ciclo del cultivo, lo cual ocurrió en detrimento de las reservas de este elemento en el suelo. La práctica de dejar o retirar los residuos de cosecha del cultivo anterior no mostró resultados concluyentes, aunque se espera que los beneficios de la misma se comiencen a observar con el transcurso de los a os. Esta práctica, al igual que la labranza cero, produjo, sin embargo, un incremento significativo de la biomasa microbiana del suelo, la cual se considera como un indicador biológico positivo de la calidad del suelo y de la sustentabilidad de los sistemas. The behavior of wheat (Triticum aestivum) in distinct rotations, tillage systems and residue management were quantified, and the mineralization and absorption of nitrogen (N) under different management conditions were measured employing microlysimeters placed in the soil. Three years after establishing treatments tending to make the wheat production system more manageable in a zone with summer rainfall, the incorporation of a legume in the rotation translated, in general, into better yields and better N supplies for the plant. This was explained by the occurence of greater mineralization of N in the soil, both during the crop’s growth period as well
A collaborative research and a teaching experience with teachers: A follow-up study of the pupils INVESTIGACION Y EXPERIENCIA DE TRABAJO COLABORATIVO CON PROFESORAS: UN SEGUIMIENTO DE LOS ALUMNOS
Eugenia Orellana Etchevers,Luis Bravo Valdivieso
Estudios Pedagógicos (Valdivia) , 2000,
Abstract: This article presents the application of a collaborative teaching model among specialists in Special Education and teachers in low S.E.S. children's groups, and a follow-up study of reading and verbal process in the First and the Second Grades. Results show significant differences in reading comprehension and in verbal test between the experimental and the control groups in the Second Grade. In the Fourth Grade, as the collaborative teaching was over, significant differences between those groups did not appear. Este trabajo da cuenta de una experiencia pedagógica colaborativa entre profesoras de aula e investigadores universitarios de Educación Especial, con alumnos de primero y de segundo a o básico, de N. S. E. bajo, pertenecientes a una Corporación Municipal de Santiago. La hipótesis general de la investigación es que mediante una colaboración entre los investigadores de la universidad y las profesoras de las escuelas, los ni os lograrán un mejor nivel de comprensión lectora y en procesos psicolingüísticos. Los resultados se alaron diferencias significativas entre el grupo experimental y el grupo control en lectura y en lenguaje, al final del segundo a o de seguimiento, a favor del primero. Estas diferencias desaparecieron en cuarto a o básico, un a o después que terminó el trabajo de colaboración con las profesoras.
Superyó: el malestar en la clínica
Laznik,David; Battaglia,Gabriel; Capurro,Elda; Etchevers,Martín;
Anuario de investigaciones , 2007,
Abstract: we intend to show the theoretical and clinical importance of the freudian concept of super-ego, by establishing its connection with lacan formulation of the big other. we take into account two fundamental and structural super-ego versions (the first one connected to the big other's structural function, the second one related to pre-edipic mother's linking in girl), as well as superego in its relationship with anxiety and transference. current clinical references (marginal situations, addictions, impulse disorders) reveal the importance of this connection, that leads to "transference handling" notion in freud and "analyst position" in lacan.
Are we giving azathioprine too late? The case for early immunomodulation in inflammatory bowel disease
María Josefina Etchevers, Montserrat Aceituno, Miquel Sans
World Journal of Gastroenterology , 2008,
Abstract: Inflammatory bowel disease (IBD) includes two entities, Crohn’s disease and ulcerative colitis. Both are chronic conditions with frequent complications and surgical procedures and a great impact on patient’s quality of life. The thiopurine antimetabolites azathioprine and 6-mercaptopurine are widely used in IBD patients. Current indications include maintenance therapy, steroid-dependant disease, fistula closure, prevention of infliximab immunogenicity and prevention of Crohn’s disease recurrence. Surprisingly, the wide use of immunosuppressants in the last decades has not decreased the need of surgery, probably because these treatments are introduced at too late stages in disease course. An earlier use of immunossupressants is now advocated by some authors. The rational includes: (1) failure to modify IBD natural history of present therapeutic approach, (2) demonstration that azathioprine can induce mucosal healing, a relevant prognostic factor for Crohn’s disease and ulcerative colitis, and (3) demonstration that early immunossupression has a very positive impact on pediatric, recently diagnosed Crohn’s disease patients. We are now awaiting the results of new studies, to clarify the contribution of azathioprine, as compared to infliximab (SONIC Study), and to demonstrate the usefulness of azathioprine in recently diagnosed adult Crohn’s disease patients (AZTEC study).
Malrotación intestinal en adultos: causa infrecuente de abdomen agudo oclusivo Intestinal malrotation in adults: infrecuent cause of acute oclusive syndrome
Josefina Etchevers,Mariano Palermo,María Gabriela Salvatore,Francisco Tarsitano
Revista Argentina de Radiología , 2008,
Abstract: El 90 % de los casos de obstrucción por malrotación intestinal ocurre en ni os menores de 1 a o de edad, siendo altamente infrecuente en adultos. Un paciente de sexo masculino, de 31 a os de edad, con antecedente de episodios de dolor abdominal, vómitos y constipación que alternaban con períodos de normalidad desde la ni ez es admitido en el hospital por sintomatología similar, la que no cede. Luego de estudios radiológicos y de laboratorio se decide su intervención quirúrgica con el diagnóstico de obstrucción intestinal. El diagnóstico intraoperatorio realizado fue de malrotación intestinal tipo I, practicándose la operación de Ladd. La evolución del paciente es favorable. La infrecuente presentación de esta patología en adultos es lo que motiva la presentación del caso. The 90 % of the bowel obstruction caused by intestinal malrotation occurred in children younger than 1 year, this type of obstruction is very uncommon in adults. This is a male of 31 years old, with history of abdominal pain, vomits and constipation since he was a child. These symptoms were sporadical, he didn't need any surgical treatment. Recently he was admitted in our institution presenting similar symptoms, without remission of them. After imaging and laboratory studies, was performed a surgery, and the intraoperatoty diagnosis was intestinal malrotation type I. The surgical treatment was the Ladd Operation. The postsurgery evolution was good. Discharged 4 days after the surgery. The aim of this article is to present a rare case of intestinal obstruction in adults caused for an intestinal malrotation.
Calidad microbiológica de leche y quesos según el suministro de diferentes silajes
Francisco Etchevers,Enzo Zamboni,Zandra Della Giustina,Adriana Gieco
Ciencia, Docencia y Tecnología , 2010,
Abstract: El objetivo del estudio que se expone fue determinar cómo influye el consumo de forrajes ensilados, debidamente caracterizados, en la calidad microbiológica de la leche producida y su aptitud para la elaboración de quesos pasta dura. La producción de las vacas se controló durante dos a os, en períodos quincenales, variando la alimentación para cada tratamiento; se extrajeron muestras de leche para analizar su calidad y se elaboraron quesos tipo "Reggianito". Los resultados mostraron que en silos de maíz "pasados" existe mayor contaminación de esporas que en silos de maíz "óptimos", en tanto que los silos de pulpa de citrus presentan contaminación mínima. No se observó correlación entre el nivel de esporas en leche y en silos. El recuento de microorganismos esporulados en los quesos no guarda relación proporcional con los encontrados en la leche utilizada como materia prima, por los cual los quesos no evidenciaron problemas durante la maduración.
Soil carbon dynamics in high-elevation temperate forests of Oaxaca (Mexico): thinning and rainfall effects Dinámica del carbono del suelo en bosques templados de elevación alta en Oaxaca (México): efectos del raleo y las lluvias
Vinisa Saynes,Jorge D Etchevers,Leopoldo Galicia,Claudia Hidalgo
Bosque (Valdivia) , 2012,
Abstract: To explore the forest harvest effects on biologically active fractions of soil organic matter dynamics, we evaluated soil total carbon (C-total) and soil microbial biomass carbon (SMBC) concentrations, and basal soil respiration (BSR) in old-growth forest (as control) and logged stands (logged one- and 20-yrs ago) in two regions (dry and wet regions) in temperate forests of Oaxaca, Mexico. Mean C-total values were higher in the Dry region than in the Wet region. Greater mean annual precipitation resulted in consistently lower BSR, but had inconsistent effects on the SMBC in dependence upon annual rainfall in the sampling year. In the dry region SMBC was higher in the dry season than in the rainy season, and BSR was higher in soils collected in the rainy season than those collected in the dry season. Forest logging consistently decreased C-total and SMBC concentrations and BSR. In contrast, rainfall seasonality in the Wet region did not affect SMBC concentration or BSR. On the other hand, in this region, the main response to the forest thinning application was an increase in the concentration of C-total. Overall, we conclude that the soil carbon pools and the effects of forest thinning on the biologically active fractions of soil organic matter will vary, depending on the details of the site's annual rainfall amount. Las concentraciones de carbono (C) total y en la biomasa microbiana del suelo (CBMS), y la respiración basal del suelo (RBS) en bosques templados naturales (testigo) y rodales con aprovechamiento (después de uno y 20 a os de la extracción), fueron determinadas en dos regiones (seca y húmeda) con bosques templados en Oaxaca, México, con el fin de explorar efectos del manejo en la dinámica de las fracciones biológicamente activas de la materia orgánica del suelo. Los valores medios de C-total fueron mayores en la región seca que en la húmeda. La mayor cantidad de precipitación media anual produjo menor RBS, pero tuvo efectos inconsistentes en la concentración de CBMS dependiendo de la cantidad de lluvia en el a o de muestreo. En la región seca, el CBMS fue mayor en la estación seca que en la de lluvias y la RBS mayor en los suelos recolectados en la estación de lluvias que en aquellos recolectados en la seca. El aprovechamiento disminuyó las concentraciones de C-total y de CBMS, y la RBS. En la región húmeda, la estacionalidad en las lluvias no afectó la concentración de CBMS ni la RBS. En esta región, la principal respuesta al raleo del bosque fue el aumento en la concentración de C-total. Se concluye que los almacenes de carbono en el suelo
Indicadores bioquímicos en suelos de un transecto altitudinal en el eje neovolcánico mexicano
Pajares-Moreno, Silvia;Gallardo-Lancho, Juan F.;Etchevers-Barra, Jorge D.;
Agrociencia , 2010,
Abstract: the biochemical aspects of the tepetates (hardened volcanic layers) and soils coming from volcanic materials have been little studied. the flow of co2 (fc) and the biochemical properties of volcanic soils representative of méxico were evaluated in this work. five soils were chosen in a transect of the tláloc volcano with different uses: cuminal grassland (pc), pine-oak (pe), reforested pine (pr), bare tepetate (td), and halophytic formations of the former lake of texcoco (lt), located at 2950, 3010, 2700, 2650, and 2220 m altitude. the soils of the transect correspond to the sequence: phaeozems (pc), luvisols (pe and pr), tepetates (td) and solonchacks (lt). in each zone soil samples were taken (0-15 cm deep) and fc and soil moisture (hs) were periodically measured in situ from august 2005 to july 2006. the variables determined were: soil organic c (soc), total n (nt), microbial biomass c and n, basal respiration (rs), ammonification of arginine, and enzyme activities (dehydrogenase, β-glucosidase, phosphatase, urease and protease). the most degraded areas (td and lt) recorded lower values in all variables, whereas the best preserved (pe and pc) showed higher values (especially in soc, nt, microbial biomass and enzyme activities). the rs and fc were low in td (8.1 ug c-co2 g-1 d-1 and 0.05-0.07 g m-2ha-1 ), since this is a hardened substrate without a plant cover and low content of soc and nt (0.8 mg c g-1 and 0.13 mg n g-1). the higher content of soc in pe and pc (55.2 and 32.7 mg c g-1) and hs during the rainfall period promote soil microbial activity and thus fc (1.22 and 1.05 g m-2 ha-1 in august). the biochemical variables selected, of easy measurement and interpretation, are suitable indicators to assess the quality of mexican volcanic soils under different environmental conditions.
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